Several solutions to the problem of extinguishing fires in confined spaces where mammalian life, in particular, human life, is present are know in the prior art. Basically, these solutions revolve around producing a habitable yet combustion suppressant atmosphere is the confined space.
U.S. Pat. No. 3,715,438 discloses a habitable atmosphere, which does not sustain combustion of flammable materials of the non-self-sustaining type and which is capable of sustaining mammalian life, consisting essentially of air; a perfluoroalkane selected from the group consisting of carbon tetrafluoride, hexafluoroethane, octafluoropropane, and mixtures thereof; and makeup oxygen in an amount from about 0 to the amount required to provide, together with the oxygen present in the air, sufficient total oxygen to sustain mammalian life. The perfluoroalkane should be present in an amount sufficient to impart to the atmosphere a heat capacity per mol of total oxygen which is sufficient to suppress combustion of the flammable materials present in the enclosed compartment containing the atmosphere. The patent also discloses a method for preventing and controlling fire in combined air-containing compartment while maintaining the compartment habitable by mammalian life, which comprises, introducing into the air carbon tetrafluoride, hexafluoroethane, octafluoropropane or mixtures thereof, in an amount sufficient to provide a heat capacity per mol of total oxygen which is sufficient to suppress combustion of the flammable materials present in the compartment and, additionally, introducing oxygen if and as required, to make up with the oxygen available in the air sufficient total oxygen to sustain mammalian life.
U.S. Pat. No. 3,840,667 discloses an oxygen-containing atmosphere which will not support combustion but will sustain mammalian life. The oxygen-containing atmosphere comprises a mixture of sufficient oxygen to sustain mammalian life; an inert, stable, high heat capacity of polyatomic (a perfluoroalkane) gas in an amount which provides the oxygen-containing atmosphere with a total heat capacity per mol of oxygen of at least 40 calories per .degree.C. measured at 25.degree. C. and constant pressure; and helium in an amount of from about 5% to the balance up to 100%. All percentages are in mol%. The atmosphere disclosed in the patent claims to be useful in sustaining mammalian life within any closed system wherein fire hazards would normally be present.
U.S. Pat. No. 3,893,514 discloses a system and method of adding nitrogen under pressure to a confined area including a habitable atmosphere to suppress a fire without any deleterious effect on humans within the environment in which the fire is suppressed. In adding nitrogen to the confined area, the partial pressure of oxygen remains the same for human life, if necessary, whereas the percent by volume oxygen is lowered to a point which is not sufficient to support combustion of burning elements. Therefore, life is sustained while the fire is suppressed without any harmful effect on humans.
Other processes and gas for extinguishing fires are taught by the following:
U.S. Pat. No. 1,926,396 discloses a process for arresting or extinguishing a flame which comprises directing into the atmosphere in the neighborhood of the flame a halogen derivative of a hydrocarbon-containing fluoride, an example being dichlorodifluoromethane.
U.S. Pat. No. 3,486,562 discloses an apparatus for detecting and extinguishing a fire in an enclosed environment. When a preselected temperature is reached in the enclosed environment, a heat sensor activates the means for evacuating the gaseous contents of the enclosed environment to an accumulator which is at a much lower pressure than the enclosed environment. At the same time, means are provided for cutting off air and power to the enclosed environment, while nitrogen is being introduced to the enclosed environment in place of the evacuated gases.
U.S. Pat. No. 3,822,207 discloses a fire-fighting composition. Chloropentafluorethane is a general purpose fire extinguishing agent of low toxicity. In a mixture with other halogenated alkanes, especially bromochlorodifluoromethane and bromotrifluoromethane, very effective extinguishing compositions may be made giving low concentrations of breakdown products in use against liquid fuel fires.
U.S. Pat. No. 3,844,354 also discloses chlorpentafluoroethane as an efficient and economic fire extinguishing agent for total flooding systems.